A taxiing system installed on an aircraft enables the aircraft, while taxiing, to travel independently of its main engines, i.e. without the main engines of the aircraft being in use.
While taxiing with an electrical taxiing system, wheels carried by one or more undercarriages are driven in rotation by actuators that include electric motors.
It is possible to make provision for an electrical taxiing system to be incorporated in an aircraft that was not fitted with such a system when it was constructed, i.e. to “retrofit” an electrical taxiing system. It is then appropriate to design an electrical taxiing system in such a manner that the modifications that need to be made to the (electrical and mechanical) interfaces of the aircraft are limited as much as possible.
Under such circumstances, the electric motors of the electrical taxiing system are powered by a pre-existing electrical power supply (e.g. an auxiliary power unit (APU)).
The pre-existing electrical power supply was initially designed to power other onboard electrical systems of the aircraft while the aircraft is on the ground, e.g. a system for steering the aircraft on the ground and a system for braking the aircraft on the ground using electrohydraulic actuators, a de-icing system, a catering system, etc. The pre-existing electrical power supply is thus of dimensions suitable for optimally powering a total load equal to a maximum nominal load.
Since all of the electrical systems powered by the pre-existing electrical power supply do not operate continuously during stages of taxiing, the pre-existing electrical power supply operates for most of the time with a total load that is less than the maximum nominal load, even when the electrical taxiing system is in operation.
Nevertheless, when the total load comes close to the maximum nominal load and an electrical system that was previously not in use is activated, then the total load becomes greater than the maximum nominal load, which runs the risk of damaging the pre-existing electrical power supply, and which reduces the effectiveness with which the electrical systems are powered by the pre-existing electrical power supply.